(1) Field of the Invention
The invention relates to power management and data transfer. More specifically, the invention relates to power management of power delivered over a bus.
(2) Background
Some prior art systems employ an uninterruptible power supply (UPS) in which an alternating current to direct current (AC to DC) converter receives an AC signal, from for example, a wall socket, and converts the signal to DC which is used to charge a battery within the UPS. A DC signal is reconverted to AC and supplied back out to connected devices. In the event of a power outage, the UPS permits an orderly shut down of the system by supplying power previously stored in the battery. Typically, external devices expect to receive 220 or 110 volts AC from a standard electrical outlet. The battery power is converted from DC to the expected 110 or 220 volts AC. Such devices typically each have their own internal AC to DC converter. Using that converter, the power supplied is again converted to DC for use in the device.
The traditional personal computer (PC) or workstation market is based on expansion capability of the unit. This has typically included such bussing structures as ISA, EISA, and PCI, as well as PCMCIA cards, all of which fall under the broad category of legacy expansion methods. Price pressures and size reduction demands have necessitated providing for relatively small number of external connectivities. The recent trend has been to move the PC in the direction of a sealed box. This trend tends to increase the relative difficulty of power management of the overall system, as well as legacy support.